A6 MMI 3G power cutting out
 

2009 A6 Avant, 160k miles. Driving back on a trip yesterday, the MMI screen went blank and zero sound- completely dead. When I stopped for a break, it came on with the ignition, then died again after an hour or so, After I got home and had to run out a few hours later, it worked fine for an hour and was working when I got home.

I'm thinking maybe a power supply/cooling fan issue- some automatic cut-out when it gets too hot? Any ideas or thoughts?

Dave